1、Designation: D4735 09 (Reapproved 2014)D4735 15Standard Test Method forDetermination of Trace Thiophene in Refined Benzene byGas Chromatography1This standard is issued under the fixed designation D4735; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers the determination of thiophene in refined benzene in th
3、e range from 0.80 to 1.80 mg/kg for theFlame Photometric Detector (FPD), and from 0.14 to 2.61 mg/kg for the Pulsed Flame Photometric Detector (PFPD). For thePFPD, the minimum level of quantitation (LOQ) is 0.14 mg/kg and the minimum level of detection (LOD) is 0.04 mg/kg, asdescribed in ASTM Resear
4、ch Report RR:D16-1038.2 The range of the test method may be extended by modifying the sampleinjection volume, split ratios, calibration range, or sample dilution with thiophene-free solvent.1.2 This test method has been found applicable to benzene characteristic of the type described in Specificatio
5、ns D2359 andD4734 and may be applicable to other types or grades of benzene only after the user has demonstrated that the procedure cancompletely resolve thiophene from the other organic contaminants contained in the sample.1.3 The following applies to all specified limits in this test method: for p
6、urposes of determining conformance to applicablespecification using this test method, an observed value or a calculated value shall be rounded off “to the nearest unit” in the lastright-hand digit used in expressing the specification limit in accordance with the rounding-off method of Practice E29.1
7、.4 The values stated in SI units are to be regarded as standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the appli
8、cability of regulatorylimitations prior to use. For specific hazard statements, see Section 7.2. Referenced Documents2.1 ASTM Standards:3D1193 Specification for Reagent WaterD1685 Test Method for Traces of Thiophene in Benzene by Spectrophotometry (Withdrawn 2009)4D2359 Specification for Refined Ben
9、zene-535D3437 Practice for Sampling and Handling Liquid Cyclic ProductsD4057 Practice for Manual Sampling of Petroleum and Petroleum ProductsD4177 Practice for Automatic Sampling of Petroleum and Petroleum ProductsD4307 Practice for Preparation of Liquid Blends for Use as Analytical StandardsD4734 S
10、pecification for Refined Benzene-545D6809 Guide for Quality Control and Quality Assurance Procedures for Aromatic Hydrocarbons and Related MaterialsE29 Practice for Using Significant Digits in Test Data to Determine Conformance with SpecificationsE177 Practice for Use of the Terms Precision and Bias
11、 in ASTM Test MethodsE260 Practice for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and RelationshipsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodE840 Practice for Using Flame Photometric Detectors in Gas Chromatograph
12、y1 This test method is under the jurisdiction of ASTM Committee D16 on Aromatic Hydrocarbons and Related Chemicals and is the direct responsibility of SubcommitteeD16.04 on Instrumental Analysis.Current edition approved Feb. 1, 2014June 1, 2015. Published February 2014July 2015. Originally approved
13、in 1987. Last previous edition approved in 20092014 asD4735 09.D4735 09 (2014). DOI: 10.1520/D4735-09R14.10.1520/D4735-15.2 Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D16-1038. Contact ASTM CustomerService at serviceastm.or
14、g.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standardsstandards Document Summary page on the ASTM website.This document is not an ASTM standard and is inten
15、ded only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the curren
16、t versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1510 Practice for Installing Fus
17、ed Silica Open Tubular Capillary Columns in Gas Chromatographs2.2 Other Document:OSHA Regulations, 29 CFR paragraphs 1910.1000 and 1910.120043. Summary of Test Method3.1 The thiophene concentration in refined benzene is determined at the milligram thiophene per kilogram sample level usingconventiona
18、l gas-liquid chromatography with a flame photometric detector (FPD) or pulsed flame photometric detector (PFPD).A reproducible volume of sample is injected. Quantitative results are obtained by the external standard technique using themeasured peak area of thiophene.4. Significance and Use4.1 This t
19、est method is suitable for setting specifications on benzene and for use as an internal quality control tool wherebenzene is either produced or used in a manufacturing process.4.2 This test method was found applicable for determining thiophene in refined benzene conforming to the specificationsdescr
20、ibed in Specification D2359 and may be applicable toward other grades of benzene if the user has taken the necessaryprecautions as described in the text.4.3 This test method was developed as an alternative technique to Test Method D1685.5. Apparatus5.1 Gas ChromatographAny chromatograph having a fla
21、me photometric detector (FPD or PFPD) may be used which canoperate at the typical conditions described in Table 1. The user is referred to Practices E260 and E355 for additional informationabout gas chromatography principles and procedures. An automatic sampler is recommended. The GC should have the
22、 followingperformance characteristics:5.1.1 Column Temperature ProgrammerThe chromatograph shall be capable of linear programmed temperature operationover a range sufficient for the separation of the compounds of interest.The programming shall be sufficiently reproducible to obtainretention time rep
23、eatability throughout the scope of the analysis.5.1.2 Sample Inlet SystemThe sample inlet system shall have variable temperature control capable of operating continuouslyat a temperature up to the maximum column temperature employed. The sample inlet system shall allow a constant volume ofsample to
24、be injected by means of a syringe. For the PFPD a heated flash vaporizing injector designed to provide a linear sample4 Available from U.S. Government Printing Office Superintendent of Documents, 732 N. Capitol St., NW, Mail Stop: SDE, Washington, DC 20401, http:/www.access.gpo.gov.TABLE 1 Thiophene
25、 in Benzene Instrumental ConditionsColumn A B C DTubing 6 ft 318 in. Ni 15 ft by 18 in. stainless steel 10 ft by 18 in. stainless steel 30 meter, Fused Silica,0.25 (or 0.32) mm IDPhase TCEEPA SP-1000 OV-351 Bonded Polyethylene Glycol(PEG/CW)Concentration, weight % 7 10 10 0.5 (or 1.0) micron film th
26、icknessSupport Chromosorb P-AWB Supelcoport Chromosorb P-AW N/AMesh 100/120 60/80 80/100 N/AGas chromatographic conditionsInlet 150 170 180 200Carrier Gas helium helium helium heliumCarrier Flow, mL/min 30 30 30 1.01.5Split Ratio N/A N/A N/A 50:1Column Temperature, C 70 90 70 50C for 1 mi., 10C/min
27、to200C, hold for 1 minDetector FPD FPD FPD PFPD(optimize flows permanufacturers instructions)(tuned for Sulfur)BG-12 Filter2 mm combustorH2, mL/min 140 140 140 11.5flow optimized for S modeAir I, mL/min 80 80 80 12.0flow optimized for S modeAir 2, mL/min 70 70 70 10.0flow optimized for S modeTempera
28、ture (C) 220 220 250 250A Tetracyanoethylated pentaerythritol or pentrile.B Chromosorb P is a registered trademark of the Manville Corp.D4735 152split injection (that is, 50:1) is required for proper sample introduction.The associated carrier gas flow controls shall be of sufficientprecision to prov
29、ide reproducible column flows and split ratios in order to maintain analytical integrity.5.2 ColumnThe column shall provide complete resolution of thiophene from benzene and any other hydrocarbon impuritiesbecause of potential quenching effects by hydrocarbons on the light emissions from the thiophe
30、ne. The columns described in Table1 have been judged satisfactory. The user is referred to Practice E1510 for assistance on installing fused silica capillary columnsinto the gas chromatograph.5.3 DetectorAny flame photometric detector (FPD or PFPD) can be used, provided it has sufficient sensitivity
31、 to produce aminimum peak height twice that of the base noise for a 4-Linjection on the FPD, or a 1.0-Linjection for the PFPD of 0.5 mg/kgthiophene in benzene. The user is referred to Practice E840 for assistance in optimizing the operation and performance of the FPD.5.4 Data Acquisition SystemThe u
32、se of an electronic integrating device or computer data system is recommended fordetermining the detector response. The device and software shall have the following capabilities: a) graphic presentation of thechromatogram, b) digital display of chromatographic peak areas, c) identification of peaks
33、by retention time or relative retentiontime, or both, d) calculation and use of response factors, and e) internal standardization, external standardization, and datapresentation.5.5 Microsyringe, 5 or 10-L capacity.5.6 Volumetric Flasks, 50, 100 and 500-mL capacity.5.7 Separatory Funnel, 1-L capacit
34、y.6. Reagents and Materials6.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are
35、available.5 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently highpurity to permit its use without lessening the accuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, reference to water shall be understood to mean reagent water conf
36、orming toType IV of Specification D1193.6.3 Carrier Gas, nitrogen, helium, or hydrogen, chromatographic grade, or shall have a purity of 99.999 % (V/V) or better.6.4 Hydrogen, zero grade, or shall have a purity of 99.999 % (V/V) or better. (WarningHydrogen is an extremely flammablegas under high pre
37、ssure.)6.5 Compressed Air, hydrocarbon-free, or shall have a purity of 99.999 % (V/V) or better. (WarningCompressed air andoxygen are gases under high pressure and they support combustion.)6.6 Cadmium Chloride Solution (20 g/L)Dissolve 20 g of anhydrous cadmium chloride CdCl2 into 200 mLof water and
38、 diluteto 1 L.6.7 Isatin SolutionAdd 0.5 g of isatin to 200 mL of chloroform. Heat under a fume hood to a temperature just below theboiling point of chloroform (61C) and maintain for 5 min with stirring. Filter the hot solution through hardened rapid-filter paperinto a 250-mL volumetric flask and di
39、lute to volume.6.8 Benzene, Thiophene-FreeWash 700 mL of benzene in a 1000-mL separatory funnel to which has been added 5 mL ofisatin solution, with successive 100-mL portions of concentrated sulfuric acid until the H2SO4 layer is light yellow or colorless.Wash the benzene with 100 mLof water, then
40、twice with 100 mLof cadmium chloride solution (CdCl2). Finally, wash with another100-mLportion of water and filter the benzene through medium filter paper into a storage bottle, stopper the bottle tightly and savefor future use. Commercial sources of thiophene-free benzene are available and can be u
41、sed as an alternative to this cleanupprocedure.6.9 Sulfuric AcidConcentrated H2SO4.6.10 Thiophene.6.11 Stock solutions of thiophene in benzene are commercially available and can be used for preparation of calibrationstandards.7. Hazards7.1 Benzene is considered a hazardous material. Consult current
42、OSHA regulations and suppliers Material suppliers SafetyData Sheets, and local regulations for all materials used in this method.5 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe Ameri
43、can Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D4735 1538. Sampling and Handling8.1 Sampling of benzene should follow safe rules in
44、 order to adhere to all safety precautions as outlined in the latest OSHAregulations. Refer to Practices D3437, D4057, and D4177 for proper sampling and handling of benzene.9. Preparation of the Apparatus9.1 The chromatographic separation of trace level sulfur compounds can be complicated by absorpt
45、ion of the sulfur compoundsby the gas chromatographic system. Therefore, care should be taken to properly free the system of active sites where absorptionor reactions could take place.9.2 Follow the manufacturers instructions for mounting and conditioning the column into the gas chromatograph and ad
46、justingthe instrument to conditions described in Table 1. Allow the instrument and detector sufficient time to reach equilibrium.10. Calibration Curve10.1 Prepare a 500-mLstock solution of thiophene in benzene at approximately the 100 mg/kg level by adding 0.04 g (38.0 L)of thiophene to 435 g (500 m
47、L) of thiophene-free benzene.10.2 Calculate the thiophene content of the stock solution according to the following equation:Thiophene,mg/kg5A 310 3!/Bwhere:A = weight of thiophene, mgB = weight of benzene, g10.3 Prepare five calibration blends ranging from 0.00 to 5.0 mg/kg of thiophene in benzene b
48、y diluting the appropriate volumeof stock solution into a known volume of thiophene-free benzene. The user is referred to Practice D4307 for assistance preparationof liquid blends for use as analytical standards.10.4 For example, an 87.0 mg/kg stock solution was prepared by dissolving 0.0378 g thiop
49、hene into 435 g of benzene.Aliquotsof 0.00, 0.75, 1.0, 2.0, and 5.0 mL of stock solution were dissolved in 100 mL of thiophene-free benzene to produce 0.00, 0.65,0.87, 1.75, and 4.35 mg/kg, respectively.10.5 Inject an appropriate amount of each solution (4.0-L for packed column or 1.0-L for capillary column) into the gaschromatograph. Integrate the area under the thiophene peak. Each standard solution and the blank should be analyzed in triplicate.Injection volumes shall be consistent and reproducible.10.6 Prepare a calibration curve by pl
